De Motu Animalium seemingly constitutes the very first treatise on biomechanics. The author, Giovanni Alfonso Borelli (1608-1679), was professor of mathematics in Pisa, where he worked with Malighi who was professor of theoretical medicine and focused Borelli's interest on the movements of living creatures. The work consists of two parts. In the first part Borelli analyses the action of the muscles, the movements of the limbs, and the activities of man and animals, including skating, running, jumping, swimming and flying. The second part deals with what is now called physiology, considered from the point of view of a mechanist: heart, blood circulation, breathing, separation of urine from blood in the kidneys, liver function, reproduction, fatigue, thirst, hunger, fever, and so on. The book shows Borelli to be a genial precursor. He expresses his opinion as a mathematician on problems which afterwards further stimulated the curiosity and endeavors of many generations of researchers.